Virtual Reality systems immerse the user in a virtual world. Essentially all visual stimulation is blocked out except that provided by a computer. Augmented Reality systems show the user a real world view with virtual graphics superimposed thereupon. Both kinds of systems have a feature in common in that they track the user's head or, as the case may be, the user's viewpoint, so that the graphics can be rendered from the user's viewpoint. When the user changes his position or moves his head, the virtual or augmented view is changed accordingly.
FIG. 1 show a schematic block diagram of an augmented reality system as may be utilized in conjunction with features of the invention. A tracker camera 10 is coupled by way of and A/D (analog to digital) converter 12 to a programmable digital computer 14. Two scene cameras 16 are coupled to computer 14. An ultrasound scanner 16, having a transducer 18, is coupled by way of an A/D converter 20 to computer 14. A head-mounted display (HMD) control unit 22 is coupled for signal interchange with computer 14 and to an HMD display 24.
Augmented Reality visualization of ultrasound images has been proposed in the literature; see for exampled, M. Bajura, H. Fuchs, and R. Ohbuchi. “Merging Virtual Objects with the Real World: Seeing Ultrasound Imagery within the Patient.” Proceedings of SIGGRAPH '92 (Chicago, Ill., Jul. 26–31, 1992). In Computer Graphics 26, #2 (Jul. 1992): 20
Helpful background material on augmented reality and related topics can be found in Proceedings of the IEEE and ACM International Symposium on Augmented Reality 2000, dated Oct. 5–6, 2000; Munich, Germany; IEEE Computer Society, Los Alamitos, Calif., U.S.A. In the above-cited Proceedings, an article of particular interest entitled AUGMENTED WORKSPACE: DESIGNING AN AR TESTBED is published on pages 47–53, and is authored by Frank Sauer, an inventor in the present application, et alii.
See also the review article by R. T. Azuma: “A Survey of Augmented Reality”, Presence: Teleoperators and Virtual Environments, 6(4), 355–386, (1997).